Question

EXERCISE 5.3
1. Find the sum of the following APs:
(1) 2, 7, 12, ..., to 10 terms.
(i) -37,-33, -29, ... to 12 terms.
1
تسمم
(m) 0.6, 1.7, 2.8,..., to 100 terms.
(iv)
.., to 11 terms.
15 12 10​

Answer 1

SOLUTION :-

By using the formula

Sn = (n/2)[ 2a+(n-1)d]

(1) S10 = (10/2) [ 2×2+(10-1)×5]

= 5[ 4+45]

= 245

(2) S12 = (12/2)[ 2×-37+(12-1)×4]

= 6[ -74+44]

= 6[ -30]

= -180

(3) S100 = (100/2)[ 2×0.6+(100-1)(1.1)]

= 50[ 1.2+99×1.1]

= 50[ 1.2+108.9]

= 50×110.1

= 5505

(4) is wrong question